Mechanical aspects of ferro-elastic behavior and phase composition of La0.58Sr0.4Co0.2Fe0.8O3−δ

Phase composition and thermo-mechanical properties of La0.58Sr0.4Co0.2Fe0.8O3−δ (LSCF) have been studied. The LSCF perovskite material comprised two phases: rhombohedral and cubic, with a ratio that showed to depend on both cooling rate as well as atmosphere. The fracture stress of LSCF was determined on the basis of ring-on-ring bending tests between room temperature (RT) and 800 °C. Below 700 °C non-linear load-displacement curves were obtained, an effect that is attributed to the ferro-elasticity of the rhombohedral phase. Both SEM and TEM verify the existence of a domain structure in the rhombohedral grains. The indentation fracture toughness appears to be insensitive to temperature variations from RT up to 350 °C. The importance of thermal history on phase composition and the resulting thermo-mechanical behavior is discussed.